Wire up Linux and Windows exports

export_presets.cfg is hand-written (no editor GUI available here): a
minimal preset per platform (name, platform, path, x86_64
architecture) is enough, since Godot fills every other option from
its platform defaults. tools/setup.sh now also fetches the matching
export templates (~1.2GB, cached outside the repo like the Godot
binary itself) -- note the directory it unpacks into uses a dot
before "stable" while .godot-version and the download URLs use a
hyphen, two different spellings of the same version that are easy to
conflate.

Both make export-linux and make export-windows now actually run and
produce a working package; tests/ and addons/gut/ are excluded from
the exported .pck (124KB vs 1.5MB before -- a dev-only dependency has
no business shipping to a child's machine). The Linux binary was
smoke-tested headless and boots cleanly; the Windows .exe could only
be confirmed as a valid PE32+ binary, since no Windows machine or
Wine is available in this environment -- flagged in
docs/testing/manual-checklist.md rather than claimed as verified.

This closes out every step in the launch prompt's "Ordre de
construction." README status lines updated to reflect the first
playable prototype rather than a bare skeleton.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

export_presets.cfg

@@ -0,0 +1,45 @@
+[preset.0]
+
+name="Linux"
+platform="Linux"
+runnable=true
+advanced_options=false
+dedicated_server=false
+custom_features=""
+export_filter="all_resources"
+include_filter=""
+exclude_filter="tests/*, addons/gut/*"
+export_path="build/linux/aventuriers_des_mots.x86_64"
+patches=PackedStringArray()
+encryption_include_filters=""
+encryption_exclude_filters=""
+encrypt_pck=false
+encrypt_directory=false
+script_export_mode=2
+
+[preset.0.options]
+
+binary_format/architecture="x86_64"
+
+[preset.1]
+
+name="Windows"
+platform="Windows Desktop"
+runnable=true
+advanced_options=false
+dedicated_server=false
+custom_features=""
+export_filter="all_resources"
+include_filter=""
+exclude_filter="tests/*, addons/gut/*"
+export_path="build/windows/aventuriers_des_mots.exe"
+patches=PackedStringArray()
+encryption_include_filters=""
+encryption_exclude_filters=""
+encrypt_pck=false
+encrypt_directory=false
+script_export_mode=2
+
+[preset.1.options]
+
+binary_format/architecture="x86_64"